At first, I thought there was something wrong with me. Like many unconventional flavours you encounter when exploring the wider beer world, I thought that getting a beer-flavoured mouthwash was normal, even expected as part of a Scotch ale (hence the 2.5 I gave the Wee Highlander). But, try as I might, I just couldn’t get on board.

Then I learnt about chlorophenols.

Contrary to popular belief, phenols aren’t just a buzzword for amateur beer reviewers but rather a class of organic compounds. Phenols are responsible for an array of interesting flavours in beers, from the cloves of a hefeweizen (4-vinyl guaiacol) to the “barnyard” aspect of a Brettanomyces-afflicted farmhouse ale (4-ethyl phenol).

Without getting buried in chemistry, chlorine – from water or sanitiser or fruit – can bond with phenols to give you chlorophenols. Chlorophenols are commonly used as pesticides, herbicides, and disinfectants, which you’ll notice is a list that doesn’t include anything that should be consumed by a human.

…all yeast produces phenolics to some degree, but some yeasts are more prone to phenol production. In particular wild yeasts and Belgian yeasts tend to produce high levels of phenols in the finished beer. At low levels this manifests itself as a clove like flavor that is desirable in many Belgian beers as well as the classic German hefeweizen. However, if too many phenols are present it may morph into a smoky or spicy flavor or even the dreaded band-aid flavor.

Although it is rare, incompletely rinsed sanitizers can produce a Band-Aid aroma of chlorophenol. This is not unconommon at bars and restaurants, as the sanitizers for glasswares or growlers are chlorinated or brominated, either of which can produce chlorophenolic flavors.

Mosher goes on to say that it “should never be detectable” and it doesn’t take a lot to ruin a beer, just 1mL in 40,000 kegs (<0.5ppb) will do it.

Finding out that chlorophenols are not desirable was both irritating and, frankly, unsurprising. Unfortunately, there are players within the beer industry who think that they can get away with either:

knowing the product is defective but nonetheless charging full price with no compensation to consumers

not doing any quality assurance on the product and releasing it to the market

I’m not sure which is worse but neither are to be tolerated. Such approaches show short-sightedness and benefit no one in the long run.

In summary, your beer shouldn’t taste like band-aids and, if it does, you deserve a refund. I wouldn’t wish chlorophenolic beer on my worst enemy.

Have you ever had a phenolic mess of a beer? If so, what was it and did you do anything about it?

I’ve recently realised that the distinction between a faulty beer and a beer you don’t like is not well understood (it’s a distinction we often fail to make), which is why defective beers end up on tap. More education is required.

If it was that easy to make chlorophenols then nature would be full of them. It isn’t. Generally it requires chlorine + phenols + 200C + 5atm pressure. A recently discovered synthesis can be done at 65C with a pure cobalt catalyst surface.

PCB was used in transformers because it had a large heat capacity and was not flammable.